If pulpal necrosis is not treated in a timely manner, bacteria can spread out of the apical foramen causing periapical inflammatory lesions, with granulation tissue proliferation being the most common, and as the granulation tissue becomes progressively larger, it becomes difficult for nutrition to support its growth, followed by necrosis, liquefaction and abscess formation. The clinical manifestation is an acute attack of chronic periapical inflammation with severe pain and continuous throbbing, accompanied by tooth loosening and abscess formation, which can break through the bone wall and mucosa for drainage and form a gingival fistula if left untreated. Clinically, root canal treatment is often recommended for teeth that can be preserved, and the fistula can subside on its own when the periapical inflammation is eliminated after perfect root canal treatment. If the tooth cannot be retained, extraction is often recommended after the tooth has entered the chronic phase and the fistula can be removed by scraping.